System and method for air handling control in opposed-piston engines with uniflow scavenging

Abstract

In an air handling system of a uniflow-scavenged, two-stroke cycle opposed-piston engine, repeatable trapped mass and composition are achieved by determining provision of air handling setpoints that control operation of the engine's air handling system components. In some aspects, these setpoints govern operations of the air handling system by actively controlling the intake manifold pressure (IMP), EGR flow, and exhaust channel backpressure.

The invention claimed is: 
     
       1. A uniflow-scavenged, opposed-piston engine, comprising:
 at least one cylinder with a bore and axially-spaced exhaust and intake ports, and a pair of pistons disposed in opposition in the bore and operative to open and close the exhaust and intake ports during operation of the engine; 
 a charge air channel to provide charge air to an intake port; 
 an exhaust channel to receive exhaust gas from an exhaust port; 
 a supercharger operable to pump charge air in the charge air channel; 
 an exhaust gas recirculation (EGR) channel having an input coupled to the exhaust channel and an output coupled to the charge air channel; and, 
 a control mechanization operable to:
 determine a plurality of air handling setpoints for trapped conditions in the at least one cylinder; 
 determine a plurality of external operating conditions of the air handling system; and, 
 adjust, based on the external operating conditions, the plurality of air handling setpoints. 
 
 
     
     
       2. The opposed-piston engine of  claim 1 , in which the control mechanization is operable to adjust a first setpoint for intake pressure in the charge air channel, a second setpoint for EGR flow in the EGR channel, and a third setpoint for fresh air flow into the charge air channel. 
     
     
       3. The opposed-piston engine of  claim 1 , in which the control mechanization is further operable to correct the air handling setpoints in response to changed engine operating conditions. 
     
     
       4. The opposed-piston engine of  claim 1 , in which the plurality of trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature. 
     
     
       5. The opposed-piston engine of  claim 4 , in which the control mechanization is operable to adjust a first setpoint for intake pressure in the charge air channel, a second setpoint for EGR flow in the EGR channel, and a third setpoint for fresh air flow into the charge air channel. 
     
     
       6. The opposed-piston engine of  claim 5 , in which the control mechanization is operable to:
 adjust intake pressure in the charge air channel by one of changing a speed of the supercharger and operating a first valve to shunt charge air flow from an output to an input of the supercharger; 
 adjust EGR flow in the EGR channel by operating a second valve to increase or decrease exhaust gas flow through the EGR channel; and, 
 adjust fresh air flow into the charge air channel by adjusting backpressure in the exhaust channel. 
 
     
     
       7. The opposed-piston engine of  claim 6 , in which the control mechanization is operable to adjust backpressure in the exhaust channel by one of operating a third valve in the exhaust channel or changing a turbine geometry in the exhaust channel. 
     
     
       8. The opposed-piston engine of  claim 5 , in which the control mechanization is further operable to correct the first, second, and third setpoints in response to changed engine operating conditions. 
     
     
       9. The opposed-piston engine of  claim 8 , in which the control mechanization is operable to:
 adjust intake pressure in the charge air channel by one of changing a speed of the supercharger and operating a first valve to shunt charge air flow from an output to an input of the supercharger; 
 adjust EGR flow in the EGR channel by operating a second valve to increase or decrease exhaust gas flow through the EGR channel; and, 
 adjust fresh air flow into the charge air channel by adjusting backpressure in the exhaust channel. 
 
     
     
       10. The opposed-piston engine of  claim 9 , in which the control mechanization is operable to adjust backpressure in the exhaust channel by one of operating a third valve in the exhaust channel or changing a turbine geometry in the exhaust channel. 
     
     
       11. An opposed-piston engine equipped with an air handling system, comprising:
 at least one cylinder with a bore, axially-spaced exhaust and intake ports, and a pair of pistons disposed in opposition in the bore and operative to open and close the exhaust and intake ports during operation of the engine; 
 a charge air channel to provide charge air to an intake port; 
 an exhaust channel to receive exhaust gas from an exhaust port; 
 a supercharger operable to pump charge air in the charge air channel; 
 an exhaust gas recirculation (EGR) channel having an input coupled to the exhaust channel and an output coupled to the charge air channel; and, 
 a control mechanization operable to:
 determine a plurality of air handling setpoints for trapped conditions in the at least one cylinder; 
 determine a plurality of external operating conditions of the air handling system; 
 change the setpoints in response to the external operating conditions; and 
 adjust, based on the changed setpoints, an intake manifold pressure in the charge air channel, an EGR flow in the EGR channel, and a backpressure in the exhaust channel. 
 
 
     
     
       12. The opposed-piston engine of  claim 11 , in which the control mechanization is operable to determine a first setpoint for the intake manifold pressure, a second setpoint for the EGR flow, and a third setpoint for the backpressure. 
     
     
       13. The opposed-piston engine of  claim 12 , in which the trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature. 
     
     
       14. The opposed-piston engine of  claim 12 , in which the control mechanization is further operable to correct the setpoints in response to changed engine operating conditions. 
     
     
       15. A method of operating an opposed-piston engine with an air handling system, comprising:
 generating exhaust gas in at least one ported cylinder of the engine; 
 transporting exhaust gas from an exhaust port of the at least one ported cylinder through an exhaust channel; 
 recirculating a portion of the exhaust gas from the exhaust channel through an EGR channel; 
 pressurizing fresh air; 
 mixing recirculated exhaust gas from the EGR channel with the pressurized fresh air to form charge air; 
 pressurizing the charge air with a supercharger; 
 providing the pressurized charge air to an intake port of the at least one ported cylinder; 
 determining a plurality of air handling setpoints for trapped conditions in the at least one ported cylinder; 
 determining a plurality of external operating conditions of the air handling system; and, adjusting, based on the external operating conditions, the plurality of air handling setpoints. 
 
     
     
       16. The method of  claim 15 , in which the plurality of trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature. 
     
     
       17. The method of  claim 16 , in which adjusting the plurality of air handling setpoints include adjusting a first setpoint for intake pressure in the charge air channel, adjusting a second setpoint for EGR flow in the EGR channel, and adjusting a third setpoint for fresh air flow into the charge air channel. 
     
     
       18. The method of  claim 17 , in which:
 in response to adjusting a first setpoint, adjusting intake pressure in the charge air channel by one of changing a speed of the supercharger and operating a first valve to shunt charge air flow from an output to an input of the supercharger; 
 in response to adjusting a second setpoint, adjusting EGR flow in the EGR channel by operating a second valve to increase or decrease exhaust gas flow through the EGR channel; and, 
 in response to adjusting a third setpoint, adjusting fresh air flow into the charge air channel by operating a backpressure in the exhaust channel. 
 
     
     
       19. A method of operating an opposed-piston engine equipped with one or more ported cylinders and a supercharger, comprising:
 generating exhaust gas in at least one ported cylinder of the engine; 
 transporting exhaust gas from an exhaust port of the at least one ported cylinder through an exhaust channel; 
 recirculating a portion of the exhaust gas from the exhaust channel through an EGR channel; 
 pressurizing fresh air in a charge air channel; 
 mixing recirculated exhaust gas from the EGR channel with the pressurized fresh air to form charge air; 
 pressurizing the charge air with a supercharger; 
 providing the pressurized charge air to an intake port of the at least one ported cylinder; 
 determining a plurality of air handling setpoints for trapped conditions in the at least one cylinder; 
 determining a plurality of external air handling conditions; 
 changing the setpoints in response to the external air handling conditions; and 
 adjusting, based on the changed setpoints, an intake manifold pressure in the charge air channel, an EGR flow in the EGR channel, and a backpressure in the exhaust channel. 
 
     
     
       20. The method of  claim 19 , in which determining a plurality of air handling setpoints includes determining a first setpoint for the intake manifold pressure, determining a second setpoint for the EGR flow, and determining a third setpoint for the backpressure. 
     
     
       21. The method of  claim 20 , in which the trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature. 
     
     
       22. The method of  claim 19 , in which determining the plurality of air handling setpoints includes correcting the setpoints in response to changed engine operating conditions.